iONic

Hello all,
I am trying to build a 12V Lead-Acid Trickle Charger, but with some added features.
I'd like a green power on LED and an LED way to monitor the Current drawn.

For example: 1 LED for 20mA, 2 LED's for 40mA, 3 LED's for 80mA, 4 LED's for 160mA, and 5 LED's for 320mA or higher. Actually it might be better to only have 1 of 5 LED's on at any given time.

Attached Images

Wall-Wart Trickle Chargers2.png (7.0 KB, 10 views)

ericgibbs

hi,
For the current LED indicator I would suggest a low value resistor in the low side of the charger rail.
An opa across the resistor, the output of the opa driving a LM3914 and LEDs, either in dot/bar mode.

Do you need a hand with the design?

EDIT: this could one way to do it.

Attached Images

ChgInd1.gif (41.0 KB, 17 views)

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
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iONic

I had thought about the LM3914 as a posible solution so this could work out nice. Thanks for the schematic and your efforts!

Would this affect the voltage requirments from the transformer(Wall-Wart)??

ericgibbs

hi,
If you allow about 10mA/LED that should cover the major part of the extra current required.
I would estimate that if the existing wall wart is say, 500/100mA, it should be OK.

You could set the LM3914 for 'dot' mode, thats one LED at 10mA!

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/